Dolphins are changing diets as waters warm, study finds

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Scientists say the endangered Māui dolphins seem to be adjusting their diets due to climate change.

Tiny skin samples taken from the animals over nearly 30 years, between 1993 and 2020, showed chemicals indicating the dolphins were switching prey as the water warmed.

Emma Carroll, associate professor of biological sciences at the University of Auckland, who co-authored the paper, said the findings help give a better idea of ​​how Māui dolphins might react to more drastic environmental changes. .

“Overall, this is good news for the Māui dolphin…they are able to find their preferred prey and so far adapt when conditions change,” she said.

The species is on the brink of extinction, with only 54 living adults.

The researchers also think the dolphins were likely at their “thermal limit” in the area they currently live in, so big changes were likely needed.

“We really hope they can continue to adapt,” Carroll said.

“It’s something that [we’ll be] look into the future; how will climate change and increased warm events like La Niña alter their food, their ecosystems, and the distribution of these dolphins.”

The timing of the changes shown in the skin samples provides clues to what was happening when the dolphins changed their diet.

Beginning in 2008, the pods’ diets became less diverse, coinciding with the point where a marine sanctuary in their range restricted fishing along a 40 kilometer stretch of the west coast of Tāmaki Makaurau.

The paper’s lead author, Courtney Ogilvy, a doctoral student at the university, said Māui dolphins mainly eat small fish under 10cm, such as chub cod, red cod and sprats. Skin samples couldn’t tell scientists exactly what species the dolphins eat – just that the range of species has narrowed.

“We believe the sanctuary has increased the amount of food available to dolphins,” Ogilvy said.

“It meant they could get more of their favorite prey and not work so hard to get many different types of food.”

The dolphins also changed their diet notably in 2015 and 2016 – but only temporarily.

This change corresponded with the timing of an El Niño weather event in 2015 and 2016, when fish that would not normally be found in such abundance in their area would have become more common due to changes El Niño could have on temperatures. water and current changes.

rnz.co.nz

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